<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            padding: 10px;
            margin: 0;
            line-height: 50px;
        }

        .con {
            width: 400px;
        }

        .circle {
            height: 50px;
            width: 50px;
            color: aliceblue;
            display: inline-block;
            border: 1px solid red;
            border-radius: 50%;
            text-align: center;
        }

        .circle:nth-child(2n) {
            background-color: rgb(0, 255, 255);

        }

        .circle:nth-child(2n+1) {
            background-color: rgb(0, 0, 0);
        }
    </style>

</head>

<body>
    <div class="con">
        <span class="circle">1</span>
        <span class="circle">2</span>
        <span class="circle">3</span>
        <span class="circle">4</span>
        <span class="circle">5</span>
        <span class="circle">6</span>
        <span class="circle">7</span>
        <span class="circle">8</span>
        <span class="circle">9</span>
        <span class="circle">10</span>
        <div class="circle">12</div>
        <div class="circle">13</div>
        <div class="circle">14</div>
        <div class="circle">15</div>
        <div class="circle">16</div>
        <div class="circle">17</div>
        <div class="circle">18</div>
        <div class="circle">19</div>
        <p class="circle">20</p>
        <p class="circle">21</p>
        <p class="circle">22</p>
        <p class="circle">23</p>
        <p class="circle">24</p>
        <p class="circle">25</p>
    </div>
</body>

</html>